Spark plug terminal connector



Sept. 4, 1956 A. J. BATTEY ETAL SPARK PLUG TERMINAL CONNECTOR Filed Feb.18, 1955 INVENTORS ALEXANDER J BATTE Y JAMES GREENE ATTORNEY SPARK PLUGTERMINAL CONNECTOR Alexander J. Battey, Skaneateles, and James Greene,Auburn, N. Y., assignors to Auburn Spark Plug Co., )gncogporated,Auburn, N. Y., a corporation of New Application February 18, 1955,Serial No. 489,067

6 Claims. (Cl. 339-26) This invention relates to spark plugs andconsists more particularly in new and useful improvements in terminalconnectors for use with spark plugs of the type employed in aircraftmotors.

These spark plugs usually include an annular spark plug shell containinga center electrode which is inset from the upper end of the shell withits upper extremity serving as the point of contact for a coil springconnected to the end of an electric wire or cable. Generally, the end ofthe cable is skinned so as to protrude into a hole in a rivet or grommetwhich in turn is electrically connected to one end of the coil spring,an insulating sleeve being provided around the end of the cable andsupporting the grommet and spring so that the whole unit can be insertedinto the upper end of the spark plug shell with the coil spring inelectrical contact with the spark plug electrode.

A number of objectionable features or disadvantages have beenencountered in the use of conventional connectors with spark plugs ofthe type here involved. One of the most troublesome of thesedisadvantages has been the failure to make intimate contact with thestranded wire of the high tension cable, due to the methods employed inconnecting the skinned wire to the eyelet of the connector. Anotherdisadvantage has resulted from the use of a conventional coil spring asthe contact memher, due to the tendency of such a spring to catch on theedge of the spark plug when removing it from the spark plug well, thuscausing the spring to stretch beyond its elastic limit which requiresreplacement of the complete unit. Ordinarily these springs are formed ofresilient wire of circular cross-section.

Still another disadvantage of conventional equipment including such acoil spring, lies in the failure of the spring to carry sufiicientcurrent and its tendency to wear under the vibration of use. A coilspring frequently rubs on the side walls in the retaining recess of theconnector and occasionally wears in two, thus requiring replacement.

It is therefore the primary object of the present invention to provide aconnector assembly for the high tension cables employed in shieldedspark plugs of the aircraft type, which overcomes all of thesedisadvantages noted in conventional equipment. To this end, we haveprovided a connector assembly including an insulator sleeve mem herhaving a transverse web or bridge extending across the lower portionthereof in upwardly spaced relation from its lower end, dividing theinterior of the sleeve into a main cable receiving compartment and acontact cup receiving recess, means being provided for retaining thecontact cup in said recess and establishing a maximum effectiveelectrical contact between the skinned wire of the cable, the connectingeyelet, and the contact cup.

Another object of the invention resides in the use of an internallywound volute spring formed of a fiat resilient metal strip, as theactual contact member, in place of the conventional circular coilspring. One of the advantages of a volute spring for this use lies inthe increased electrical contact available between the component parts.

nited States atent O1 Furthermore as the volute spring is compressed, aprogressively greater area of contact is made between the cup and theterminal of the spark plug which eliminates heating by poor electricalcontact which in some instances has burned the round helical spring intwo.

Still another object of the invention is to provide an improved means ofconnecting the skinned end of the wire to the connecting eyelet bycrimping the latter around the wire.

With the above and other objects in view which will appear as thedescription proceeds, the invention consists in the novel featuresherein set forth, illustratedin the accompanying drawings and moreparticularly pointed out in the appended claims.

Referring to the drawings in which numerals of like character designatesimilar parts throughout the several views,

Figure 1 is an elevational view partly broken away, showing therelationship of the connector, to the spark plug and its centralelectrode.

Figure 2 is an exploded view of the assembly, showing the sleeve, cupand eyelet in section, and

Figure 3 is an enlarged transverse sectional View showing the wellportion of a spark plug insulator with the connector assembly and cablein place, the cable being shown in elevation, and the spark plug shellomitted.

In the drawing, referring first to Figure 1, a conventional aircraftspark plug is generally represented by the numeral 4 and includes theusual shell 5 with its insulator 5 forming a cable connecting well 6 forhousing the center electrode '7 of the spark plug. The upper end of theshell 5 is reduced and externally threaded as at 8 to receive thecoupling nut 9 on one end of elbow 16 which receives the high tensioncable to be connected to the plug. The opposite end of the elbow to isprovided with a similar connecting collar lit, by means of which it isconnected to a conventional ground shielding 12 surrounding the cable.The cable consists of a central conductor 13 enclosed in an insulatingsheath 14. in this figure, the coupling nut 9 is shown disengaged fromthe threads 3, to more clearly illustrate the relationship of theconnector assembly to be described.

The component parts of the connector assembly will best be seen fromFigure 2. A cylindrical sleeve 15 composed of steatite, alumina, teflonor other suitable material, iorms the main supporting element of theconnector assembly. Adjacent its lower end the interior of the sleeve 15is provided with a transverse partition or web member 16, formedintegrally therewith and defining within the sleeve a cable receivingcompartment 17, open at its upper end, and a. connector cup receivingrecess 18 opening at the lower end of the sleeve. The partition 16 isprovided with a central aperture 19 adapted to receive the upper end ofa grommet or eyelet generally indicated by the numeral 20, for securingthe inverted connector cup 21 in the recess 18 and embracing the skinnedend 13a of the high tension wire 13 in intimate electrical contact aswill later appear.

The connector cup 21 is of a diameter to fit closely within the recess18 and its transverse or base wall is provided with an opening 22adapted to register with the opening 19 in the partition 16 when theinverted cup is inserted in the recess 13. The annular side wall of thecup 21 may extend axially a slight distance beyond the annular boundingwall of the recess 18, with its edge turned inwardly as at 23 to form anannular lip for retaining the volute spring in place as will be seenfrom Figure 3.

The eyelet or grommet 20 comprises a tubular body portion, one end 25 ofwhich is of a diameter to fit through the opening 22 in the cup 21 andthe registering opening 19 in the partition 16, its bore 26 being of adiameter to receive the skinned end 13a of the high tension wire 13. Thegrommet 20 is provided with a radial flange 27, spaced a sufficientdistance from the extremity of the end portion 25, to provide a shankwhich projects slightly beyond the inner face of the partition 16 whenthe flange 27 is in abutment with the under side of the base wall of cup21 in the assembled positions of these components, so as to permit theprojecting extremity 25 to be flared outwardly around the edges ofopening 19, in the nature of a rivet. A predetermined area of thetubular grommet, between the flange 27 and the opposite end of thegrommet is of reduced thickness as at 28 to facilitate the crimping ofthe skinned end 13a of the wire 13 when the device is assembled.

The volute spring element 24 is formed of a flat strip of any suitableresilient metal, preferably inconel, and is internally Wound clockwiseor counterclockwise from its top convolution 29 so as to form adownwardly projecting spiral, maintaining a constant tendency to expandboth radially and axially from a contracted coiled condition. In otherwords, when the reduced lower convolution 30 is turned in the samedirection it is wound and simultaneously forced upwardly, the springretracts itself within the confines of the upper convolution 29 which inturn is contracted to a sufficiently reduced diameter to fit within thecup 21. Upon release of the spring it expands radially until theperiphery of the top convolution 29 engages the inner wall of the cup,the lip 23 or" the cup engaging the lower edge of the convolution 2? andretaining the same in place as the remaining convolutions expand andproject axially of the spring.

In the assembly of the connector, the annular flange 27 of the eyelet ispreferably although not necessarily welded to the under side of the basewall of the cup 21 to insure intimate electrical contact between the cupand eyelet which is most important for this assembly. The cup 21 is theninserted in the bottom recess 18 of the sleeve 15 with its transversebase wall in close contact with the under side of the web or partition16 and the opening 22 in the cup, registering with the opening '19 inthe web. The upper end 25 of the long eyelet 20 projects throughregistering openings 19 and 22 and its upper extremity is flared orcrimped outwardly over the top surface of the web 16 around the opening19.

The insulating sheath is then removed from the high tension cable 13 asat 13a, leaving a skinned area of a length equal to the length of thecrimped rivet. The stranded wires 13a are then pushed into the bore 26of the rivet as the cable end is inserted into the upper compartment 17of the sleeve 15. The thinned section 28 of the eyelet is then crushedaround the stranded wires as at 28a in Figure 3, holding them inintimate electrical contact with the eyelet. This operation may beaccom* plished by the use of any suitable crimping tool or pliers, thejaws of which are inserted within the open end of the cup 21, a forcebeing used in the crushing operation which will hold against a specifiedpull on the cable. Thus, a positive solderless connection is maintainedwhich will not be affected by heat, high current impulses, ozone or theproducts of ozone and moisture.

Next, the volute spring 24 is turned manually in the same direction asit is wound as previously explained, and its contracted top convolution29 is snapped into the cup 21 where it is retained against axialmovement, by the inturned lip 2.3. Upon release, convolutions of thspring expand both radially and axially and maintain a constant downwardtension on the lower or contact convolution 30. The assembled connectorand cable are then inserted in the well 6 of the spark plug 4, until thelower convolution 30 of the volute spring 24 contacts the upper end ofthe center electrode 7 which projects upwardly a slight distance withinthe well 6, whereupon, the terminal nut 9 is screwed on to the threads 8on the shell 5 to retain the connector in place.

It will be noted that as the volute spring 24 is compressed against thecontact element of center electrode 7,

a progressively greater area of contact is made between the cup and theterminal of the spark plug, thus eliminating heating by poor electricalcontact which as before stated, in some cases has burned theconventional round helical spring in two. Furthermore, the area of theflat volute spring is greater than the conventional coil spring and as aresult, will carry more current.

It will thus be seen that the present invention is far more practical,economical and efficient than those previously known. The use .of thevolute spring eliminates the tendency of rubbing on the side walls ofthe well of the connector and therefore the spring cannot wear through.The volute spring can be easily placed in or removed from the cup by asimple action of twisting the spring in the direction it is wound as thespring is pushed into the cup which causes the coils to wind tighter andthe diameter to become smaller. However, once in the cup, the springunwinds to its normal diameter with the result that there is no dangerof the spring falling out.

Furthermore, by crimping the long eyelet around the lead wires, morearea of contact is obtained, giving better electrical contact than thatprovided by bending the strands of lead wire over the standard shorteyelet. At high energies and current, bent over wires burn through dueto poor contact and unless exceptional care is taken in bending theconducting strands of the high tension cable around the end of theeyelets, these strands will interfere with the spring action. Thisdisadvantage is impossible with the present invention, involving thewire crimped within the eyelet.

A further advantage lies in the possible salvage value, as the volutespring can be replaced without separating the combination cup and eyeletfrom the lead assembly, whereas, when the conventional coil spring isused the assembly is made inoperative when the spring is worn out andthe complete unit must be destroyed. When the combination cup and eyeletassembly is a permanent part of the sleeve as in the present invention,the volute spring can be replaced without separating the sleeve from thelead assembly, making it unnecessary to scrap the sleeve.

From the foregoing it is believed that the invention may be readilyunderstood by those skilled in the art without further description, itbeing borne in mind that numerous changes may be made in the detailsdisclosed without departing from the spirit of the invention as setforth in the following claims.

I claim:

1. A sparkplug terminal connector, comprising an insulating sleeveadapted to receive an electrical cable through one end, a transverse webspaced inwardly from the opposite end of said sleeve and definingtherein an annular recess, an inverted metal cup in said recess with itsbase wall abutting the under side of said web, registering openings inthe central portions of said base wall and web to receive the conductorof said cable, common means cooperating with said web for retaining saidcup in said recess and establishing fixed electrical contact between thecup and said conductor, said common means comprising an elongatedeyelet, having a substantially centrally located radial flange adaptedto abut the under side of the base wall of said cup when one end isinserted through said registering openings, the extremity of theinserted end of said eyelet being outwardly crimped over said web toform a retaining flange, binding the cup within the recess in tightengagement with said web, said radial flange maintaining electricalcontact between said eyelet and cup, the bore of said eyelet receivingthe end of the conductor of said cable in electrical contact therewith,and a partially radially compressed volute spring inserted in said cupand retained in electrical contact therewith, solely by its own radialexpanding tension, with its diminishing convolutions projecting axiallyfrom said cup and terminating in a contact end for electrical engagementwith a spark plug center electrode.

2. A spark plug terminal connector as claimed in claim 1 wherein saidradial flange is welded to the base wall of said cup.

3. A spark plug terminal connector as claimed in claim 1 wherein saideyelet is crimped around said conductor to maintain electrical contact.

4. A terminal connector for use with a spark plug of the type includinga central electrode housed within an annular open-ended insulated shell,comprising an insulating sleeve adapted to be inserted within saidinsulated shell, a transverse partition defining in said sleeve a cablereceiving compartment open at one end and a coaxial connector cupreceiving recess opening at the opposite end of said sleeve, an invertedmetal connector cup in said lastnamed recess, registering openings inthe base wall of said cup and said partition, a tubular eyelet, one endof which is insertable in said registering openings in electricalcontact with said cup, means associated with said eyelet and partitionfor securing said cap in said recess, an electric cable terminating atone end Within said compartment and having its conducting Wiresprojecting into the bore of said eyelet, means establishing electricalcontact between said wires and eyelet, and a volute spring, one end ofwhich is insertable in said cup in electrical contact therewith, itsdiminishing convolutions being projected axially from said cup underspring tension and terminating in a contact end adapted to engage andestablish electrical contact with the center electrode of said sparkplug, in said insulated shell.

5. A terminal connector as claimed in claim 4 wherein said eyelet iscrimped around said conducting wires, and is provided with a radialflange welded to the base wall of said cup, whereby intimate electricalcontact is maintained between said conducting wires, eyelet and cup.

6. A spark plug terminal connector comprising an insulating sleeveadapted to receive an electric cable through one end, an inverted metalcup inserted in the opposite end of said sleeve, means securing said cupin said sleeve in electrical contact With the conductor of said cable,and a partially radially contracted, internally wound, volute springformed of a flat resilient metal strip, readily insertable and removablewith respect to said cup and adapted to be retained in electricalcontact with said cup, solely by its own radial expanding tension, withits diminishing convolutions projecting axially from said cup andterminating in a contact end for electrical engagement with a spark plugcenter electrode.

Mosthaf Aug. 14, 1945 Rennie July 18, 1950

